Piston



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ORIGINAL FILED 056.19, 1917.

Patented Jan. 2, 1923.

UNITED STATES PATENT OFFICE.

FREDERIC A. PARKI-IURST, OF CLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO ALUMINUM MANUFACTURES, INCORPORATED, OF CLEVELAND, OHIO,

A CoRroRATIoN or DELAWARE.

PISTON.

Original application filed December 19, 1917, Serial No. 207,836. Divided and this application led September 10, 1920. Serial No. 409,304.

To aZZ whom 'it may com'ern Be it known that l, Fnnonluo A. PARK- HURs'r, a citizen ot the United States. residing at Cleveland. in the county ot Cuyahoga. and State ot' Ohio, have invented certain new and useful Improvements in listons, of which the following is a specification. reterencebeinghad therein to the accompanying drawings.

This invention relates to pistons Jfor i11- ternal combustion engines, the invention having to do `more especially with pistons of the type shown in the patent to Spillman and Mooers, No. 1,092,870.

One object of the invention is the production of a piston of the type lastretcrred to formed of metal of low specific gravity,

such as a suitable aluminum alloy, and having an internal structure and other physical characteristics which mark Such alloys when cast in permanent molds.

Another object of the invention is the production of an improved piston ot' the type referred to of such character that complicated core work is obviated.

A further object'of the invention is theI production of an improved piston ofthe type in question having a form and constituent material such that it can he formed either in whole or in part h v (l) casting and (2) further shaping the cast structure by drawing, spinning, rolling or other form of sWaging operation.

Pistons of the type in question comprises a head part with an end wall and a cylindrical side Wall; and a guide part or trunk having an inner wall, which is preferably formed vwith wrist pin bosses, and an outer cylindrical, cylinder-engaging wall. vWhile pistons of this type may he made by various processes, an improved process has been described and claimed in my copending application, No. 207,836, filed December 19, 1917, of which this application is a division. Briefiy stated, my improved process consists of making a piston casting ot metal capable of being swaged, with the metal of either or both the side wall of the head and the outer wall of the trunk in the form of an outwardly extending fiange, and thereafter by spinning or other swaging operation, turning such flange or flanges to cylindrical conformation. By such a method,

the original casting is simplified to such an extent thatit is possible to produce it in a permanent mold and thus give the metal of the finished piston physical characteristicsv which are peculiar to the rapid chilling ot' the permanent mold.

For the purpose of explaining the chal'- acter of my improved piston and the process of'producing it, Iliave -illustrated in the accompanying drawings several forms of construction and have indicated the. succes! sive steps in carrying out the proce-ss.

In the drawings, Fig. 1 is a side elevation, partly in section, ot a piston casting which represents the first step of my improved process.

Fig. 2 is a central vertical section ot' the same piston casting after a portion of the flange which is to formthc outer wall ot' the trunk has been machined away preparatory to the next step of the process.

Fig. 3 is a view similar to that of Fig. 2 but showing outwardly extending fiange spun upward to form the cylindrical outer wall of the trunk.

Fig. 4 is a view similar to that of Fig. 3, but showing the piston after the removal by machining of superfiuous metal.

Fig. 5"s a view similar tothe last. showing the piston completed by machining operations. 4 f

Figs. 6 and 7 are side elevation and hottom plan, respectively, of the finished piston.

Fig. 8 is a side elevation` partly in section, of a piston illustrating a modified form of construction.

Fig. 9 is afragmentary side elevation,

partly in section, illustrating the first stepA in the process of making the piston shown in Fig. 8. 7

Fig. 10 is a central vertical section of a piston illustrating still another form of construction. y y

Fig. 11 is a fragmentary side elevation partly in section illustratingthe first step in the process of making the piston shown in Fi 10.

Re erring now in detail to the form of construction illustrated in Figs. 5, 6, and 7 1 designates the head part or" the piston in its entirety. and 2 designa-tes the trunk part of the piston in its entirety. YThe head 1 comprises an end Wall 1 and a side wall l", while the trunk or guide part of the piston has an inner wall or section 2 and an outer cylinder-engaging wall 2b.` The trunk or O'uide part of the piston preferably also per orms the function of connecting the piston to the connecting rod and to that end is formed with wrist pin bosses 2C, 2d, the latter boss being formed with an enlargement 2e to receive the usual set screw. rlhe head and trunk are also preferably formed with strengthening and heat dissipating ribs 2f 2g.

In its finished form, the lateral wall of the piston head is provided with grooves 3 to receive the usual packing rings l(not shown), and said lateral wall has a diameter such that it never closely fits the engine cylinder. v

The youter wall 2" of the trunk is connected with the inner wall thereof only at its lower end, so that heat conducted from the end-'wall of the piston head must traverse the entire length of the piston before reaching the outer guide wall 2b, and therefore much of this heat is dissipated by radiation and Contact with the air and vapors of the crank case before it reaches said outer wall 2b, so that said outer wall is maintained at a relatively low temperature and can, therefore, fit relatively closely in the engine cylinder.

Preferably, a ,series of holles 4, 4 are formed at the. bottom of the piston between the inner wall 2a and the outer wall 2b to permit lubricant and oil which enters the space between said walls to drain 'freely back to the crank case.

In the production ofV the piston illus'- trated in Figs. 5, 6 and 7, the first step, in accordance with my improved process, is thev making of the casting shown in Fig. 1.

This casting is preferably formed-of ametal 0fv low specific gravity Such as the aluminum `alloys now extensively employed in the making of pistons and in a suitable. permanent mold. I preferably employ a mold and process such as is setforth in Letters Patent 1,296,589, granted to Joseph H. Bamberg and such as is illustrated also in Letters Patent 1296,596 granted to me, both dated March 4th, 1919. When a suit'- able aluminum alloy is cast in molds of the charactenreferred to, the metal of the casting ascompared with the same metal cast in molds of relatively low conductivity is givenvahard, fine grained, ductile structure with excellent swaging, machining and bearing qualities, is capable of taking a high polish, and "also has remarkable strength.

To make possible the use of a permanent mold, I cast the outer wall 2b of the piston trunk in the form of a heavy outwardly extending flange 2b, and I preferably also form the casting with an internal rib or flange 5 which extends continuously around the piston directly in line with the flange 2b. The. end wall of the piston head may be formed with a work spotu 6 to facilitate subsequent machining operations, said work spot being later removed.

After the production ofthe casting, as shown in Fig. 1, the next step in my process is the machining away of the lower part of the flange 2bv and preferably the slight reduction of its diameter to form the flange 2b shown in. F ig. 2.

Thel third step in my improved process is the spinning of the flange 2b upward to form the cylindrical outer wall 2b of the piston trunk, as shown in Fig. 3. During the spinning operation, the unturned rib or flange 5 serves to greatly stiffen the piston structure so that the pressure of theI pin and the other usual finishing opera-v tions, gives the finished piston shown in Figs. 5, 6, and 7. I

' In machining the outer side wall of the piston, as has been indicated, ,the outer diameter of the wall 2b is made such that said wall has a relatively close fit in the engine cylinder whilethe side wall 1b of the head has a loose fit, the wall 2b being relied upon to guide the piston in its movement in the cylinder. f

By means of my improved process I not only avoid the complicated core work incident to the casting of prior pistons of this type, but also have produced an integrally cast .piston having .the advantages peculiar to pistons of this type with the added advantages of light weight and thehereinbefore mentioned physical characteristics peculiar to aluminum alloys cast in permanent molds.

Turning to the form of construction illustrated in Fig. 8, the finished piston comprises a head part designated in its entirety by 11 and a trunk part designated in its entirety by 12. The head comprises an end wall 11a and a cylindrical side wall 11". This latter sidewall is formed, in the present case, independently of the trunk of the piston which comprises an inner wall 12a and a cylindrical outer wall 12b, the said inner wall joining'the end wall of the piston head at points radially inside of said side wall 11b of the head, while the outer wall 12b is connected .with the inner wall only at the lower end of the piston. The inner wall of' thc pistontrunk is preferably formed with wrist pin bosses 12, 12d, the last named boss being formed with a set screw enlargement 12e.

The inner wall of the trunk and the end wall of the head are formed with strengthening and heat dissipation ribs 12212, 12h.

The sid-e wall 11b is formed in the usual manner with grooves 13 to receive packing rings and preferably also with lubricant grooves 14 also a suitable number of lubricant apertures 15 areprovidcd at the bottom of the piston and the outer wall 12b of the trunk is recessed at 16 to permit the entry of the wrist pins in the bosses 12, 12d.

In the production of the` piston shown in Fig. 8, the first step, in accordance with my process is the formation of the casting shown in Fig. 9, this casting being formed of suitable aluminum alloy or other metal in permanent molds as has been set forth in connection with the first form of construction. In this casting` it will be observed that the metal of the nished side walls 11- and 12b are in the form of outwardly extending flanges 11b and 12" respectively. After the machining or trimming of flange 11" to the form indicated by the dotted lines, it and the lower fiange 12b are spun or otherwise worked downward and upward respectively, to form the cylindrical side walls 11b and 12b, and thereafter trimming and machining `operations are carried out similar or analogous to those described in con.

nection with Figs. 1 to 7, resulting in the finished piston shown in Fig. 8.

"The construction shown in Fig. 1() is in many respects similar to that shown in Fig. 5 and comprises a head part 21 having an end wall 21a-and a cylindrical side Wall 21h, and a guide or trunk part 22 having an inner wall 22a and a cylindrical outer wall 22". The inner wall of the trunk is formed with Wrist pin bosses 22C, 22d, the boss 22d having a set screw enlargement 22 and internal ribs 22 and 22g are provided as in the first form of construction. The side wall 21b is formed with the usual grooves 23 for packing rings, a series of lubricant apertures 24 are provided at the bottom of the lshoulder 26 affords a firm abutment for the metal of the flange as it is spun inward -and' upward, as will readily be understood.

The trimming and machiningoperations subsequent to the spinning operation are similar in this case to'those described in connection with Figs. 1 to 7 and need not be further referred to. y

I have herein referred to the use of metals or metallic alloys of low specific gravity and it is to be understood that I 4mean by theseterms metals or alloys whose specific gravities are low in comparison with that of iron. the metal of which pistons have commonly been made in the past.

It will be understood that the foregoing description of certain embodiments of my invention is not intended to define or limit the invention but is presentedfor purposes of explanation and illustration, the scope of the invention being indicated by the fol'- lo-wing claim.

lhat I claim is:

An aluminum alloy piston of the trunk type having ahead section comprising an end wall and a cylindrical side Wall, and a trunk section comprising an inner wall and a cylindrical cylinder-engaging outer Wall,

said cylinder-engaging outer wall being formed of metal characterized by having a swaged structure, the said head section and the inner wall of the trunk sections being integral and formed of metal characterized by havingv a fine grained structure characteristic of aluminum alloys cast in permanent molds.

In testimony whereof I hereunto affix my signature.

FREDERIC A PARKHURST. 

